The present invention relates to a method for selecting an improved catalyst composition and a hydrocarbon compound conversion process utilizing the catalyst selected.
The improved catalyst composition selected by the present invention comprises a crystalline molecular sieve material having a structure and properties whereby the catalyst composition has at least one active catalytic site with a Mono Alkylation Selectivity Factor (hereinafter more particularly described) greater than or equal to 0 kcal/mol±0.5 kcal/mol, and optionally further at least one active catalytic site with an Olefin Oligomerization Suppression Factor (hereinafter more particularly described) greater than or equal to 5±0.5 kcal/mol.
The method of the present invention for selecting an improved catalyst composition comprising a porous crystalline material for use in a hydrocarbon conversion process comprises the steps of determining the Mono Alkylation Selectivity Factor of one or more catalyst compositions, and selecting a catalyst composition which has at least one active catalytic site with a Mono Alkylation Selectivity Factor greater than or equal to 0 kcal/mol±0.5 kcal/mol. The method may further comprise the steps of determining the Olefin Oligomerization Suppression Factor of one or more catalyst compositions, and selecting a catalyst composition which has at least one active catalytic site with an Olefin Oligomerization Suppression Factor greater than or equal to 5 kcal/mol±0.5 kcal/mol. The selected improved catalyst is beneficially selective and may be used to effect various chemical conversions, and is particularly valuable for use in an alkylation process for producing alkylaromatics, particularly ethylbenzene and cumene.
Of the alkylaromatic compounds advantageously produced by the present process utilizing the selected catalyst, ethylbenzene and cumene, for example, are valuable commodity chemicals which are used industrially for the production of styrene monomer and coproduction of phenol and acetone, respectively. In fact, a common route for the production of phenol comprises a process which involves alkylation of benzene with propylene to produce cumene, followed by oxidation of the cumene to the corresponding hydroperoxide, and then cleavage of the hydroperoxide to produce equimolar amounts of phenol and acetone. Ethylbenzene may be produced by a number of different chemical processes. One process which has achieved a significant degree of commercial success is the vapor phase alkylation of benzene with ethylene in the presence of a solid, acidic, ZSM-5 zeolite catalyst. Examples of such ethylbenzene production processes are described in U.S. Pat. No. 3,751,504 (Keown), U.S. Pat. No. 4,547,605 (Kresge) and U.S. Pat. No. 4,016,218 (Haag). U.S. Pat. No. 5,003,119 (Sardina) describes the use of zeolites X, Y, L, Beta, ZSM-5, Omega, and mordenite and chabazite in the synthesis of ethylbenzene. U.S. Pat. No. 5,959,168 (van der Aalst) describes the use of zeolites Y, Beta, MCM-22, MCM-36, MCM-49 and MCM-56 in the synthesis of ethylbenzene in a plant designed for use of aluminum chloride-based catalyst.
Another process which has achieved significant commercial success is the liquid phase alkylation for producing ethylbenzene from benzene and ethylene, since it operates at a lower temperature than the vapor phase counterpart, and hence tends to result in lower yields of by-products. For example, U.S. Pat. No. 4,891,458 (Innes) describes the liquid phase synthesis of ethylbenzene with zeolite beta, whereas U.S. Pat. No. 5,334,795 (Chu) describes the use of MCM-22 in the liquid phase synthesis of ethylbenzene; and U.S. Pat. No. 7,649,122 (Clark) describes the use of MCM-22 in the liquid phase synthesis of ethylbenzene in the presence of a maintained water content. U.S. Pat. No. 4,549,426 (Inwood) describes the liquid phase synthesis of alkylbenzene with steam stabilized zeolite Y. U.S. Patent Publication No. 2009/0234169 A1 (Pelati) describes the liquid phase aromatic alkylation over at least one catalyst bed containing a first catalyst modified by inclusion of a rare earth metal ion.
Cumene has been produced commercially by the liquid phase alkylation of benzene with propylene over a Friedel-Craft catalyst, particularly solid phosphoric acid or aluminum chloride. Zeolite-based catalyst systems have been found to be more active and selective for propylation of benzene to cumene. For example, U.S. Pat. No. 4,992,606 (Kushnerick) describes the use of MCM-22 in the liquid phase alkylation of benzene with propylene.
Other publications show the use of catalysts comprising crystalline zeolites for the conversion of feedstock comprising an alkylatable aromatic compound and an alkylating agent to alkylaromatic conversion product under at least partial liquid phase conversion conditions. These include U.S. 2005/0197517A1 (Cheng); U.S. 2002/0137977A1 (Hendrickson); and U.S. 2004/0138051A1 (Shan) showing the use of a catalyst comprising a microporous zeolite embedded in a mesoporous support; WO 2006/002805 (Spano); and U.S. Pat. No. 6,376,730 (Jan) showing the use of layered catalyst; EP 0847802B1; and U.S. Pat. No. 5,600,050 (Huang) showing the use of catalyst comprising 30 to 70 wt. % H-Beta zeolite, 0.5 to 10 wt. % halogen, and the remainder alumina binder.
Other such publications include U.S. Pat. No. 5,600,048 (Cheng) describing preparing ethylbenzene by liquid phase alkylation over acidic solid oxide, such as MCM-22, MCM-49, MCM-56, Beta, X, Y or mordenite; U.S. Pat. No. 7,411,101 (Chen) describing preparing ethylbenzene or cumene by liquid phase alkylation over acidic solid oxide, such as PSH-3, ITQ-2, MCM-22, MCM-36, MCM-49, MCM-56 and Beta at conversion conditions including a temperature as high as 482° C. and pressure as high as 13,788 kPa; and U.S. Pat. No. 7,645,913 (Clark) describing preparing alkylaromatic compounds by liquid phase alkylation in a multistage reaction system over acidic solid oxide catalyst in the first reaction zone having more acid sites per unit volume of catalyst than the catalyst in the second reaction zone at conversion conditions including for ethylbenzene a temperature as high as 270° C. and pressure as high as 8,300 kPa, and for cumene a temperature as high as 250° C. and pressure as high as 5,000 kPa. U.S. Patent Publication No. 2008/0287720 (Clark) describes alkylation of benzene over catalyst of the MCM-22 family material in a reaction zone having water content maintained at from 1 to 900 wppm. U.S. Patent Publication No. 2009/0137855 (Clark) describes a mixed phase process for producing alkylaromatic compounds from a dilute alkene feedstock which also includes alkane impurities. In the latter publication, the volume ratio of liquid to vapor in the feedstock is from 0.1 to 10.
Existing alkylation processes for producing alkylaromatic compounds, for example, ethylbenzene and cumene, inherently produce polyalkylated species as well as the desired monoalkyated product. It is therefore normal to transalkylate the polyalkylated species with additional aromatic feed, for example benzene, to produce additional monoalkylated product, for example ethylbenzene or cumene, either by recycling the polyalkylated species to the alkylation reactor or, more frequently, by feeding the polyalkylated species to a separate transalkylation reactor. Examples of catalysts which have been used in the alkylation of aromatic species, such as alkylation of benzene with ethylene or propylene, and in the transalkylation of polyalkylated species, such as polyethylbenzenes and polyisopropylbenzenes, are listed in U.S. Pat. No. 5,557,024 (Cheng) and include MCM-49, MCM-22, PSH-3, SSZ-25, zeolite X, zeolite Y, zeolite Beta, acid dealuminized mordenite and TEA-mordenite. Transalkylation over a small crystal (<0.5 micron) form of TEA-mordenite is also disclosed in U.S. Pat. No. 6,984,764.
Where the alkylation step is performed in the liquid phase, it is also desirable to conduct the transalkylation step under liquid phase conditions. However, by operating at relatively low temperatures, liquid phase processes impose increased requirements on the catalyst, particularly in the transalkylation step where the bulky polyalkylated species must be converted to additional monoalkylated product without producing unwanted by-products. This has proven to be a significant problem in the case of cumene production where existing catalysts have either lacked the desired activity or have resulted in the production of significant quantities of by-products such as ethylbenzene and n-propylbenzene.
Although it is suggested in the art that catalysts for conversion of feedstock comprising an alkylatable aromatic compound and an alkylating agent to alkylaromatic conversion product under at least partial liquid phase conversion conditions are composed of a porous crystalline aluminosilicate molecular sieves having an MWW structure type, the present catalyst selection method and improved process has remained elusive. Selecting a commercially acceptable catalyst for such processes conducted under at least partial liquid phase conversion conditions which increases monoselectivity, i.e., providing lower di- or polyalkyl product make, and does not significantly affect conversion would allow capacity expansion in existing plants and lower capital expense for grassroots plants. Unfortunately, the pore size and shape of crystalline molecular sieve components of catalyst compositions cannot adequately explain which catalyst compositions function as most effective selective aromatic alkylation catalysts. According to the present invention, it has now unexpectedly been found that an alkylation process for producing alkylaromatics conducted in the presence of a specific catalyst, selected by the present method, comprising a porous crystalline molecular sieve material, e.g., a crystalline aluminosilicate zeolite (“crystal”), having a structure and properties, whereby the catalyst composition has at least one active catalytic site with a Mono Alkylation Selectivity Factor greater than or equal to 0 kcal/mol±0.5 kcal/mol, and optionally further at least one active catalytic site with an Olefin Oligomerization Suppression Factor greater than or equal to 5 kcal/mol±0.5 kcal/mol, yields a unique combination of activity and monoselectivity. This is especially the case when the process involves at least partial liquid phase alkylation for manufacture of ethylbenzene or cumene.